1. Field of the Invention
The present invention relates to a device for detecting metal targets in general and, more particularly, for detecting metal targets, such as unexploded ordnance (UXO), underground utilities, landmines buried in the soil or otherwise visually obscured.
2. Description of the Related Art
In a variety of situations, it may be desirable to determine whether metal objects exist that are obscured from view in some manner. The objects could include buried cables, such as power or communications cables. Other objects could include buried unexploded ordnance. The objects could be buried under ground or visually obscured in other manneis, such as by a portion of a structure.
Unexploded ordnance (UXO), and particularly land mines, represent a tremendous worldwide problem. Many people are killed and maimed through encounters with unexploded ordnance. Additionally, areas where UXOs are present may not be utilized for other activities, such as agriculture and housing, among others. As a result, UXO causes human pain and suffering, displaces people and results in great expenditures for health care and loss of arable land.
Addressing the UXO problem is a worldwide concern. The process of searching for and identifying UXO is a costly, dangerous, tedious and time consuming process. For example, the US Government has estimated that UXO clearance in the United States may cost as much as 300 billion dollars and could take as long as 100 years to resolve at the present funding level.
Currently, two primary search methods exist for UXO and land mine clearance. These include human-towed or hand-carried sensor systems and special vehicles designed to pull or push large and cumbersome sensor carts. These methods have several drawbacks. Among the drawbacks are the high cost for human operators and vehicle systems. Also, operator fatigue is an issue with both methods. For example, cold and hot weather can adversely affect human operators. Additionally, both methods expose operators to danger in hostile environments. For example, operators may be exposed to live munitions, animals, harsh terrain and bad weather. Furthermore, human operators may make mistakes in navigation. Use of the known methods is typically limited to daylight working hours, since as vision is diminished the dangerous work may become significantly more dangerous. Even after encountering all of these hazards, the known methods do not provide any real time information to ensure that the test area was properly surveyed or that the sensor was operated correctly.
While some proposals have been made to automate the process of UXO detection, for example the system described in U.S. Pat. No. 6,026,135 to McFee, these proposals have been large, cumbersome and costly vehicle systems including towed sensor carts. It would be desirable to have a system for automating the process of detection of UXO.
The present invention provides a device operative to detect metal objects. The device includes a transmitter, an upper transmitter coil and a lower transmitter coil operatively connected to the transmitter. A current fed through the upper transmitter coil and the lower transmitter coil generates a field that excites eddy currents in metal objects in the vicinity of the upper transmitter coil and the lower transmitter coil. An upper magnetic field detector and a lower magnetic field detector are operative to sense eddy currents generated in the metal objects. Processor elements operatively connected to the upper magnetic field detector and the lower magnetic field detector collect, store and analyze the eddy currents and thereby automatically determine the likelihood that a metal object has been detected. A navigation system operatively connected to the processor elements controls movement of the device. Transporting elements operatively connected to the navigation system support the device and permit alteration of a position of the device.